Method for determining the degree of wear of a valve, and apparatus for carrying out said method

ABSTRACT

A method for determining the degree of wear of a valve, the degree of wear of the valve being dependent on the degree of wear of an operating element that is made of an expandable material and performs a mechanical movement each time the temperature changes, the change in temperature resulting in wear, the operating element made of an expandable material being mechanically connected to a piston; the movements of the operating element (3) made of an expandable material are calculated by initially sensing the change in temperature on the operating element (3), whereupon the changes in temperature are recalculated as movements on the basis of the temperature/expansion curve applicable to the operating element (3) made of an expandable material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/507,294, filed Feb. 28, 2017, which is a National Stage ofInternational Application No. PCT/EP2015/025063, filed Sep. 1, 2015,which claims priority from German Patent Application No. 10 2014 012688.9, filed Sep. 1, 2014, the contents of all of which are incorporatedherein by reference in their entirety.

The invention relates to the determination of a prospective or alreadyactually occurred degree of wear of a valve, for example a multi-wayvalve.

Located inside a multi-way valve is a piston, which can occupy differentpositions. The ratio as to how the medium flows through the multi-wayvalve changes depending on the position of the piston. The position ofthe piston is changed in a temperature-dependent manner by a so-calledexpandable material operating element which is connected mechanically tothe piston.

The expandable material operating element expands corresponding to atemperature/movement curve with an increase in temperature and contractsagain when the temperature drops.

These temperature-dependent movements lead to wear. Inside the multi-wayvalve, the expandable material operating element is the element upon thedegree of wear whereof the function of the valve is particularlydependent.

Manufacturers of multi-way valves of the known type have values acquiredempirically from past experience for the operating conditions of amulti-way valve and deduce therefrom how long an expandable materialoperating element can remain in use in a multi-way valve until the wearlimit of the expandable material operating element has probably beenreached.

On the basis of the period in use of a multi-way valve in a coolingcircuit, it is assumed that, after a certain period in use, the wear ofthe expandable material operating element has, with a certain degree ofprobability, advanced so far that it is advisable, for the purpose ofcontinued operational reliability of the multi-way valve and of thesystem in which the multi-way valve is present, to replace thatcomponent in the multi-way valve in which the expandable materialoperating element is contained. There are also multi-way valves, whereinthe expandable material operating element can alone be replaced.

The known multi-way valves have a removable cover. The replacement ofthe wearing parts can take place in a relatively simple and rapid mannerwhen the cover is removed.

Multi-way valves with an expandable material operating element are usedin cooling circuits. A plurality of such multi-way valves are oftenpresent in complex cooling circuits.

The actual wear of the individual expandable material operating elementsin the individual multi-way valves of a cooling circuit is in practiceoften different from the theoretical values for a trouble-free period inuse that are indicated by the manufacturers. During maintenance work onthe cooling circuits, it is difficult to ascertain what the individualactual wear of the individual expandable material operating element inthe given multi-way valve is at the present time. Both below-average andabove-average wear is possible.

In the case of complex cooling circuits, the maintenance schedules oftenassume, for safety reasons, an above-average wear and make provision forthe early replacement of all wearing parts in all the multi-way valves.The drawback with this is that wearing parts are also replaced in suchmulti-way valves in the case of which the wearing parts have not yetactually reached the wear limit.

However, the case may disadvantageously arise where the actualindividual operating conditions of a multi-way valve can lead to wear ofthe expandable material operating element that is well above average orthe expandable material operating element fails on account of a defectindependent of wear, as a result of which the multi-way valve in turnfails before the time for the replacement provided according to schedulehas arrived. Unexpected disruptions and/or damage in the system in whichthe multi-way valve is incorporated can thus detrimentally arise.

The expandable material operating element is a wearing part inside thevalve, the actual degree of wear whereof cannot hitherto be ascertainedduring the ongoing operation. The valve has to be opened and theexpandable material operating element removed for a diagnosis of theactual degree of wear. The opening of the valve and the removal andchecking of the expandable material operating element are time-consumingand labour-intensive work despite the removable cover. The function ofthe valve is no longer available during this work, so that this workcannot take place in a running system, which in turn gives rise to costson account of the shutdown of the system.

DE20120609U1 is known from the prior art. This document describes adiagnostic device for a fluid-technical device, for example a valvedevice. One or more sensors, which are assigned to the valve and delivervalues, are disclosed there. On the basis of these values, the presumeddegree of wear on the valve is calculated with the aid of empiricallydetermined comparative values. The calculation of the presumed degree ofwear of the known fluid-technical device takes place for example bycounting work cycles of the fluid-technical device. The counting of thework cycles alone does not permit a sufficiently reliable conclusion tobe drawn as to the wear on the valve, it therefore being proposed toacquire further wear-relevant parameters. With the aid of all theacquired parameters, a conclusion as accurate as possible regarding thewear is intended to be drawn on a statistically empirical basis.

The prior art does not disclose any teaching for determining the actualdegree of wear of a valve. The reference to an expandable materialoperating element and to the typical problems with an expandablematerial operating element are also wholly absent in the prior art. Areference to taking account of a temperature/movement curve as aparameter in the calculation of the degree of wear is not contained inthe prior art.

It is the problem of the invention to provide a method and apparatus forcarrying out the method, as a result of which it is possible todetermine the actual wear of an expandable material operating elementwhile it is located in a multi-way valve and without the multi-way valvehaving to be opened or dismantled.

This problem is solved by the features of the claimed invention.

The invention hereby adopts the knowledge that each movement of theexpandable material operating element is caused by a change in thetemperature of the expandable material operating element. As a result ofthermal conduction, a change in temperature of the fluid or mediumflowing through the valve also causes a change in temperature of theexpandable material operating element. The conclusion drawn from this isthat each change in temperature of the fluid or medium also causes amovement of the expandable material operating element.

During operation of the multi-way valve, a continuously updated valuefor a covered distance results from the permanent adding-up of theabsolute value of all the movements. The manufacturer of the expandablematerial operating element can indicate relatively accurately thecovered distance up to the wear limit being reached.

As described above, each change in temperature of the fluid ormedium—irrespective of whether the temperature rises or againfalls—causes a movement of the expandable material operating element bya certain distance.

According to the invention, the permanent changes in temperature of theexpandable material operating element and the temperature/movement curveapplicable to the expandable material operating element are used as adata base for determining the precise covered distance.

The temperature/movement curve applicable to the expandable materialoperating element can exhibit hysteresis and, according to theinvention, the course of the hysteresis can also be taken into account,whether the change in temperature is taking place in the rising orfalling direction, in order to determine the covered distance.

Together with the manufacturer's specification of the total covereddistance being guaranteed, a comparison of the currently determinedcovered distance with the guaranteed total covered distance enables aconclusion to be drawn as to how far the expandable material operatingelement is from the wear limit.

This advantageously permits a conclusion to be drawn concerning the wearthat is based on current measured values and calculations. The methodaccording to the invention has the advantage over the known method, inwhich the conclusions concerning wear are based on the time in use andempirically determined values.

A further advantage of the invention is that of individually measuringthe time that has passed until a specific covered distance has beenreached. This permits a predictive conclusion as to how quickly the wearlimit will be reached.

When this covered distance has exceeded a specific threshold value, asignal can be generated which can then be used for planning maintenancework.

Depending on the application and/or the place of use of the multi-wayvalve, the threshold value from reaching of which a signal is generatedfor the planning of maintenance work can be determined individually. Forexample, if a multi-way valve is located at a point of use and a certainamount of time is required to reach this point of use, the thresholdvalue can be set correspondingly lower.

A further element of the invention is to indicate the presumed degree ofwear not on the basis of the sum of all the movements detectedquantitatively over a period of time, but rather on the basis of acurrent measurement which immediately provides information as to how theexpandable material operating element is behaving at present.

There is an applicable temperature/movement curve in respect of theexpandable material operating element, said temperature/movement curvebeing able to be obtained from a data sheet or, according to theinvention, ascertained by measuring device 8 itself.

It can be verified by a correlation of the measured temperature valueand the simultaneously measured position of piston 2 whether theexpandable material operating element 3 is still expanding andcontracting such as it corresponds to the temperature/movement curveapplicable to the expandable material operating element.

A deviation of the measured position of the piston from the positionwhich would result from the temperature/movement curve is also anindication of wear. In the case of creeping wear, the deviationincreases in the course of time.

Wear that has actually occurred can thus advantageously be detected. Athreshold value can also be defined as to what deviation can still betolerated.

In the case of a deviation above the tolerated value, a signal can begenerated and/or maintenance work initiated.

According to the invention, the determination of thetemperature/movement curve applicable to the expandable materialoperating element can take place for each multi-way valve by means ofthe inventive sensors and/or evaluation electronics themselves. Thisleads to still more accurate results than when a general curve, e.g.from the manufacturer's data sheet, is used, since scatter can becompensated for.

When the individual curve is created in the case of a new multi-wayvalve or after the replacement of the expandable material operatingelement, a correlation between the temperature of the expandablematerial operating element and the position of the piston is recordedand stored for future calculations. A position is stored in respect ofeach discrete temperature value. A plurality of data pairs arepreferably recorded and stored over the entire temperature range to beexpected.

In order to take account of hysteresis effects, provision is madeaccording to the invention to record these data pairs when the change intemperature between two data pairs has a rising tendency and again torecord data pairs when the change in temperature has a falling tendency.

In order to assess the deviation of the actual piston position from theapplicable temperature/movement curve, account is therefore also takenof whether the change in temperature has a rising or falling tendency.

A possible example of embodiment of the invention is explained ingreater detail below with the aid of a FIGURE.

FIG. 1 shows multi-way valve 1 according to the invention in across-sectional schematic representation.

A piston 2 is arranged in multi-way valve 1, said piston being able tobe moved axially by means of an expandable material operating element 3.

Multi-way valve 1 has an inlet opening 4 into which a medium can flow.Depending on the position of piston 2, the medium can flow out throughone of two outlet openings 5 or 6. There are also positions of piston 2at which the medium can flow out in part from outlet opening 5 and inpart from outlet opening 6.

The expandable material operating element 3 is a wearing part andmulti-way valve 1 therefore has a cover 7 by means of which theexpandable material operating element 3 can be replaced. Cover 7 can beremoved in a non-destructive manner.

According to the invention, a measuring device 8 with sensors 9, 9 a, anindicator 10 and optionally also evaluation electronics and optionallyan energy source are housed in this cover 7.

The housing of measuring device 8, position sensor 9, the temperaturesensor and optionally further components in cover 7 has the advantagethat an existing multi-way valve, in which the existing cover is removedfor the routine replacement of the expandable material operatingelement, can be quickly and easily retrofitted with the invention. Forthe purpose of retrofitting, a new cover 7 according to the invention isfitted in place of the old cover.

Cover 7, at its outer side, optionally has an optical indicator 10,which displays the current degree of wear of the expandable materialoperating element 3. It is also possible to house an acoustic indicator10 in cover 7. Indicator 10 can emit a signal when the wear limit of theexpandable material operating element 3 or a threshold value still lyingbefore the actual wear limit is exceeded. Indicator 10 is particularlyadvantageous in complex cooling circuits, since it can quickly bedetected optically or acoustically during maintenance work whether amulti-way valve, and if so which one, requires maintenance. It is alsopossible for measuring device 8 to emit a signal in the event of adeviation.

Measuring device 8 can comprise, apart from position sensor 9 and thetemperature sensor, further sensors, for example a second positionsensor 9 a or a pressure sensor.

Position sensor 9 can detect the given axial position of piston 2. Assensor principles, both contactless sensor principles are possible, forexample inductive or capacitive, magnetic position measurement, opticalposition measurement or ultrasound position measurement. It is alsopossible for the position of piston 2 to be provided by mechanicalcoupling with a potentiometer or a variable capacitor.

In addition to the axial position determination of piston 2, it is alsopossible with the two position sensors 9 and 9 a to detect a lateralplay in piston 2. Such a lateral play in piston 2 leads, in both sensors9 and 9 a, to a quantitatively equal change in the measured value, butone that differs in respect of the sign. A lateral play in piston 2joint with the expandable material operating element 3 is a furtherindication of the fact that the expandable material operating element 3is exhibiting wear.

The temperature sensor measures the current temperature of the medium inmulti-way valve 1. The temperature of the expandable material operatingelement 3 follows this change in temperature of the medium with acertain time-lag, which in turn leads to a movement of the expandablematerial operating element 3. The expandable material operating element3 expands with a rise in temperature, whilst said expandable materialoperating element 3 contracts with a fall in temperature. Piston 2connected mechanically to the expandable material operating element 3changes its position corresponding to the change in temperature.

On the basis of a temperature/movement curve applicable to theexpandable material operating element 3, the expansion and contractionof the expandable material operating element 3 can be determined solelyfrom the permanent changes in temperature of the medium. The degree ofwear of the expandable material operating element 3 can be calculatedfrom the sum of all the expansion and contraction movements.

The temperature/movement curve applicable to the expandable materialoperating element 3 can be obtained from a data sheet or can bedetermined according to the invention by means of measuring device 8itself. In this regard, in the case of a new valve or after thereplacement of the expandable material operating element, a correlationbetween the temperature of the expandable material operating element andthe position of piston 2 is recorded and stored for future calculations.A position is stored in respect of each discrete temperature value. Aplurality of data pairs over the entire temperature range to be expectedare preferably recorded and stored.

In order to take account of hysteresis effects, provision is madeaccording to the invention to record these data pairs when the change intemperature between two data pairs has a rising tendency and again torecord data pairs when the change in temperature has a falling tendency.

It can be verified by a correlation of a measured temperature value andthe simultaneously measured position of piston 2 whether the expandablematerial operating element 3 is still expanding and contracting such asit corresponds to the temperature/movement curve applicable to theexpandable material operating element.

A deviation from the temperature/movement curve is also an indication ofwear. Wear can thus advantageously be detected that has actually alreadyoccurred and, what is more, before the quantitative sum of all thechanges has exceeded the empirically determined value from which thesignal is generated that is normally used for the planning ofmaintenance work.

Multi-way valve 1 or individual parts of multi-way valve 1 can also bemade of a non-metallic material, for example plastic or ceramic. If, forexample, piston 2 is made of a non-metallic material, a measurementmethod is then used which can detect the movement of a non-metallicmaterial, for example by means of a capacitive measurement method.

In the case of a multi-way valve 1 the housing of which is made of anon-metallic material, the measuring device can be fitted externally onmulti-way valve 1 and does not need to be housed in cover 7. This hasthe advantage that the measuring device can be retrofitted during theongoing operation of the multi-way valve.

In the case of a multi-way valve made of a non-metallic material, it isalso possible to detect by means of a suitable measuring device whethermetal particles are present in the fluid or medium.

The invention claimed is:
 1. A method for determining the degree of wearof a valve including an expandable material operating element that ispresent inside the valve, and a piston connected mechanically to theexpandable material operating element, mechanical movements of theexpandable material operating element leading to wear in the expandablematerial operating element, the method comprising: detecting changes intemperature of the expandable material operating element, converting thechanges in temperature into movements by a certain distance of theexpandable material operating element on the basis of a predeterminedtemperature/movement curve, determining a continuously updated value fora covered distance of the movements by continuously adding-up theabsolute value of the distance of all the movements, calculating adegree of wear of the expandable material operating element from thevalue for the covered distance of the movements.
 2. The method accordingto claim 1, further comprising: generating a signal when a value for thecovered distance of the movements caused by changes in temperature isexceeded, the signal can be used for planning of maintenance work. 3.The method according to claim 1, further comprising: measuring atemperature of the medium flowing into the valve with a temperaturesensor.
 4. An apparatus for determining the degree of wear of a valve,comprising: an expandable material operating element present inside thevalve, a piston moveable by the expandable material operating element,one or more sensors arranged inside or outside the valve, and evaluationelectronics; wherein the sensors deliver values to the evaluationelectronics; wherein the evaluation electronics are configured to carryout the method according to claim
 1. 5. The apparatus according to claim4, wherein one of the one or more sensors is a temperature sensor, bymeans of which the changes in temperature of the expandable materialoperating element or the change in temperature of the fluid flowingthrough the valve can be detected.
 6. The apparatus according to claim5, wherein the fluid surrounds the expandable material operatingelement.
 7. The apparatus according to claim 4, wherein the evaluationelectronics are connected to an optical or acoustic indicator.
 8. Theapparatus according to claim 4, wherein the evaluation electronicscomprises a signal output for information regarding the degree of wearof the expandable material operating element.